| 摘要 |
A pneumatic booster includes a valve mechanism for introducing atmospheric air into a variable-pressure chamber in accordance with the movement of a plunger, propelling a power piston due to differential pressure generated between the variable-pressure chamber and a constant-pressure chamber and transmitting force by which the power piston is propelled through a valve body to an output shaft. The valve mechanism includes a poppet valve mechanism including a seal surface capable of abutting against an annular atmospheric valve seat formed in the plunger and a seal surface capable of abutting against an annular negative pressure valve seat formed on an inner surface of the valve body. The annular atmospheric valve seat of the plunger is located in a position forward in a direction of propelling of the power piston relative to the negative pressure valve seat and is substantially aligned with the negative pressure valve seat in an axial direction. The poppet valve mechanism has a main poppet valve including the seal surface capable of abutting against the negative pressure valve seat and a sub poppet valve including the seal surface capable of abutting against the atmospheric valve seat. The seal surface of the sub poppet valve is spaced apart in the axial direction from the seal surface of the main poppet valve.
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